1. Field of the Invention
The invention relates generally to a solenoid valve that outputs hydraulic fluid on the basis of an exciting current applied to a coil, and more specifically to a solenoid valve having a strainer that blocks entry of foreign matter into the solenoid valve.
2. Description of Related Art
There is a conventional solenoid valve that includes a shaft-shaped spool valve housed in a tubular sleeve so as to be movable in its axial direction, and that is configured such that a flow passage of hydraulic fluid and a flow passage area are changed by moving the spool valve in the axial direction. In some solenoid valves of this type, a strainer that blocks entry of foreign matter is arranged at a supply port for the hydraulic fluid (see, for example, Japanese Patent Application Publication No. 2006-258161 (JP 2006-258161 A).
The strainer described in JP 2006-258161 A has an arc-shaped filter portion and a pair of engaging portions. The engaging portions are engaged with engaged portions formed in a strainer-attached portion of the sleeve. The strainer-attached portion is formed in a U-shape so as to surround the spool valve.
The sleeve is fitted in a fitting hole formed in a valve body, and the hydraulic fluid is supplied into the supply port through a supply passage of the valve body. In the solenoid valve described in JP 2006-258161 A, the strainer-attached portion is formed so as to be asymmetric with respect to the central axis of the sleeve. As a result, the central axis of the sleeve may be offset from the central axis of the fitting hole of the valve body due to the hydraulic pressure of the hydraulic fluid supplied to the supply port.
If the central axis of the sleeve is offset from the central axis of the fitting hole of the valve body, the amount of leakage of the hydraulic fluid is increased. With an increase in the amount of leakage of the hydraulic fluid, the load on an oil pump that discharges the hydraulic fluid increases.